1. Field of the Invention
This invention relates to deck panels that span, and are supported upon, adjacent load beams above a floor on a cargo carrying vehicle.
2. Background Art
Load beams are commonly used in cargo carrying vehicles to define a support for cargo above a main, upwardly facing floor surface. Exemplary load beams are shown in U.S. Pat. No. 7,578,644. The load beams span the width of the storage space and have ends that are releasably connected, one each, to spaced side walls that bound the storage volume. The beams are placed at controlled fore-and-aft intervals to provide stable support for spanning deck panels upon which cargo is placed.
Designers of these panels focus on a number of different criteria. First and foremost, the panels must have the ability to stably support cargo and so that it is maintained in place without significant shifting occurring relative to the underlying beams with an associated vehicle in motion.
Heretofore, many of the deck panels have been made from plywood. While plywood panels are functionally adequate, the use of plywood has a number of drawbacks.
Plywood that has a thickness adequate to support heavy loads is generally quite heavy, particularly when stored outside where it is prone to absorbing moisture through rain, snow, etc. Those responsible for loading vehicles must maneuver sheets that are typically on the order of four foot square. Aside from the weight, each panel, by reason of its large footprint, is difficult to handle, particularly for a single individual who must somehow effect a grasp on the edges thereof while maneuvering the panel to elevate it, transport it, and place the same strategically upon the load beams.
The flat surfaces of plywood are also relatively smooth. As a result, the lower surfaces on the installed plywood panels have a tendency to shift relative to underlying beams. At the same time, cargo tends to shift along the upper surfaces of the panels. Thus, appropriate provision must be made to confine both shifting of the panels themselves and the loads thereon.
Plywood panels are also difficult to maneuver individually from a stacked relationship. That is, while the plywood panels stack compactly in a face-to-face relationship, it may be difficult to grasp the individual panels to separate them from the stack.
Plywood panels are also prone to degradation, particularly after repeated use. Plywood that is not adequately dried tends to buckle. Plywood also has a tendency to splinter, which not only affects its integrity but also creates weakened areas and loose splinters that may interfere with comfortable handling by a user. Separated wood fragments may have to be collected regularly in the storage space and from adjacent loading areas. Plywood may also weaken or fail after repeated bending under load.
Generally, since plywood is made with laminated layers, a progressive compromising of the individual layers may lead to weakening or failure.
Still further, plywood is inconvenient to dispose of in an ecologically appropriate manner once it has reached the end of its useful life. Commonly, the spent plywood panels will simply be stacked in a manner whereby, in significant accumulation, they become obtrusive and unsightly.
It is known to make panels from an injection moldable plastic material to address certain of the above problems. An example of such a panel is shown in U.S. Pat. No. 6,910,668.
Many of the above problems are still contended with using panels injection molded from plastic, and the like. Molding in a contour that keys the panels against shifting relative to underlying beams stabilizes the panel mounting. However, this keying structure interferes with compact stacking of the panels where they are staged or stored.
Further, conventionally used injection molding materials create a low friction surface on the top of the panels. Thus, loads tend to shift easily against such surfaces and steps must be taken to positively secure cargo thereon.
Conventional configurations of these injection molded panels typically make them less than convenient to handle, particularly for a single individual. That is, handling involves much the same technique as handling the plywood panels, discussed above. For a single individual, this is not a convenient process.
While injection molded panels generally may have a longer anticipated useful life than those made from plywood in most applications, eventually the panels will be worn or replaced, which necessitates disposal of the old panels. Commonly, materials used to injection mold the panels are not biodegradable. Thus, disposal of large volumes of molded panels has a detrimental environmental impact.
The injection molding processes used in the past have commonly been carried out utilizing a polymer that flows readily in a heated state. These polymers tend to be brittle at low temperatures. The panels made with these polymers have thus been prone to fracturing and breakage when utilized in cold environments. Once compromised, these panels must be discarded to avoid a potentially dangerous failure in use. Early failure of these panels also has a significant economic impact that makes them impractical in certain environments and for certain heavy loading.
Another problem with prior art panels, made either from plywood or molded material, is that they are generally not stackable in a manner that facilitates bulk transportation, as around a yard using a forklift, or the like. Since plywood stacks face-to-face, there is no practical way to introduce the leading ends on the forks on a lift between panels without inflicting damage thereupon. While molded panels have raised elements that produce spacing between adjacent stacked panels, the inability of the panels to consistently nest in a predetermined manner results in their being unstably stacked. Attempts to introduce forks between adjacent panels may cause upper panels to fall off of the lifted stack.
In spite of the fact that the transportation industry utilizes very large numbers of these panels, the industry has contended with the above problems because there have been no viable commercial designs that are capable of effectively meeting the many design criteria. The industry continues to seek out panel designs that have a long useful life and are maneuverable, light in weight, stable in operation, and environmentally friendly.